Overturning of Freestanding Blocks Exposed to Earthquake Excitations 2: Shake Table Validation

Matthew D. Purvance, Abdolrasool Anooshehpoor, & James N. Brune

Published 2006, SCEC Contribution #1039

A series of shake table experiments have been carried out at the University of Nevada, Reno Large Scale Laboratory to investigate the overturning potential of freestanding blocks. Experiments consisted of scaling acceleration time histories (uniaxial forcing) so that the peak accelerations ranged from one-tenth the acceleration of gravity to the point where all of the objects on the shake table overturned three times. Objects tested ranged in height from approximately 20 cm to 120 cm and in height-to-width ratios from about 2 to 10. The acceleration time histories utilized included strong motion recordings of the 1979 Imperial Valley, 1985 Michoacan, 1999 Duzce, 1999 Chi-Chi, and 2002 Denali Earthquakes along with synthetic acceleration time histories (full sine pulse and random vibration waveforms). These results have been compared with the overturning predictions developed in the companion paper. These results confirm that both the lower- and high-frequency ground motion amplitudes contribute to overturning. The overturning predictions agree with the responses of objects with simple contact conditions. Objects with complex contact conditions, similar to precariously balanced rocks, overturn when exposed to lower amplitude ground motions than predicted. A methodology is developed and demonstrated to account for complex contacts via nondestructive tilting tests, providing robust estimates of their overturning responses. These results validate the use of the companion formulation to assess the overturning potential of freestanding objects with both simple and complex basal contact conditions.

Purvance, M. D., Anooshehpoor, A., & Brune, J. N. (2006). Overturning of Freestanding Blocks Exposed to Earthquake Excitations 2: Shake Table Validation. Earthquake Engineering and Structural Dynamics,.